Hi Luigi,
> yes, but the point is that perhaps I can find another
> chain like
> \opOp{\opSimple{\opMouv{\opAp
> and have another stack overflow.
Sorry I can't understand the meaning.
The file mptextmp.tex which was ok contains the line
\opOp{\opSimple{\opMouv{\opAp{titi}}}}%
Best,
Akira